1. Field of the Invention
The invention relates to a three-dimensional molded body and a method for producing an adhesive bond between a polymer-containing material and a three-dimensional molded body having an inorganic porous surface structure.
2. Description of the Prior Art
Molded bodies primarily of polymer-containing materials are produced by flow processes, pressing and/or sintering processes by known methods. Conventional shaping methods include thermoplastic processing of liquid polymer-containing materials. However, these methods require that the materials to be processed have a sufficiently low melt viscosity. Although the melt viscosity of some polymer-containing materials can be reduced by high process temperatures to such an extent that thermoplastic shaping is possible, the technical complexity required for such process temperatures is much higher than that for lower process temperatures. Furthermore, the polymer-containing material may decompose at least partially at high process temperatures, and the greater temperature difference which is to be overcome in cooling from high process temperatures to room temperature in comparison with lower process temperatures leads to greater volume shrinkage. Important materials having advantageous properties, for example, polymers having a high degree of polymerization, such as that often exhibited by polytetrafluoroethylene or polyethylenes or microphase-separated block copolymers cannot be processed thermoplastically because of their high melt viscosity at all temperatures at which these materials do not decompose at least partially to a substantial extent.
Some attempts to solve these problems have been made such as use of essentially known sintering methods for production of molded PTFE bodies. These usually include the introduction of small particles of the material to be shaped into a mold and partial bonding of these particles by subsequent heating. Sintering methods are associated with great changes in volume which is a circumstance which raises problems associated with manufacturing, in manufacturing precision parts, such as to produce medical implants. The molded parts obtained by this method are usually porous and have only unsatisfactory mechanical properties.
Another strategy for producing molded parts of materials that cannot be processed thermoplastically is to use machining techniques in which material is mechanically removed from a monolith until the desired molded part is obtained. Such machining techniques are naturally associated with a substantial amount of reject material machined off of the molded part, which in turn raises disposal problems, while on the other hand being a disadvantage economically, in particular in the shaping of expensive high-performance polymers.
The processing of polymer solutions by so-called flow processes offers only limited possibilities for production of molded parts having mechanical stability because other problems are associated with this process technology. For example, large quantities of organic solvents are required to convert polymer components to a soft or dissolved state in which further processing is possible, but these organic solvents are usually toxic as well as being extremely problematical environmental pollutants, ultimately leading to disposal problems that cannot be disregarded. Furthermore, physical phenomena that are technically difficult to handle, such as phase separation, hydrodynamic instabilities or the like, occur during processing of polymer solutions due to evaporation of the solvent, and these phenomena can have a permanent and virtually uncontrollable influence on the properties of the molded parts and coatings produced by the flow process technology. In this context, the uncontrolled development of cavities, voids and pores in the molded parts comprised of polymer materials can be mentioned as typical phenomena in this context. Dissolving of polymer-containing materials in solvents often takes much longer than dissolving materials having a low molecular weight. Furthermore, the solubility of polymers in solvents is often very low. For many polymer-containing materials having advantageous properties such as polymers having a high molecular weight such as PE, the dissolving rate in all solvents and the solubility are so low that industrial processing of polymer solutions is almost impossible in these cases. There are no known suitable solvents for many other polymer-containing materials having advantageous properties such as PTFE.
In addition, no composite materials with polymer-containing materials, which cannot be processed thermoplastically, can be produced by the methods described above. This would be advantageous because, on the one hand, due to the inexpensive filler, the corresponding amount by volume of expensive high-performance polymers could be eliminated, for example, while on the other hand the properties of the polymer-containing material could be advantageously modified in a composite.
In addition to the production-related problems mentioned above, molded parts containing fluorinated polymers in particular, for example, molded parts made of PTFE are subject to so-called cold flow in which a gradual change in shape of the respective molded body occurs due to creep phenomena even at room temperature.
Furthermore, reference is made to two publications which describe methods by which pores or cavities within a porous matrix structure are filled with another substance. For example, DD 132 426 A describes a method for rapid impregnation of dry or moist finished parts comprised of porous construction materials, preferably based on concrete or plaster. To do so, an impregnating agent in solid form, for example, in the form of paraffin granules or paraffin-bitumen granules, is added to the concrete or plaster composition, which is to be provided as the starting material for production of a corresponding finished part. This composition is sent for a suitable shaping and then drying process, during which pores develop within the construction composition as it solidifies, but these pores are ultimately clogged at an elevated drying temperature by the paraffin granules and/or paraffin-bitumen granules entering into the melt. Finished parts manufactured by the technical teaching according to DD 132 426 A unavoidably have air inclusions inside the regions filled with paraffin granules and/or paraffin-bitumen granules. The method that can be derived from DD 132 426 A does not allow processing of the polymer-containing material at temperatures below the temperatures required for thermoplastic processing.
CH 690 175 A5 describes a method by which a porous layer on an object, which is not otherwise porous, is filled by solutions or suspensions containing polymers under fluctuating pressure conditions. The use of both solutions and suspensions requires a solvent whose presence makes the impregnation process technically complicated, especially since solvents must be removed from the impregnated layer and ultimately must be disposed of at great expense. Furthermore, volatile components alter the material properties of polymers in a manner that is difficult or impossible to control. Furthermore, the filling factor of the polymer within the specimens is less than 100%, so it is impossible to fill the pores completely with polymer.